The present invention relates generally to corrosion sensing and in particular to methods and apparatus for providing visual display indicative of extent of corrosion of a material of interest.
Sensitive material and equipment are often located in or exposed to corrosive environments. Corrosion damage to such material and equipment can cause serious operational difficulties and economic loss. In certain mission-critical and lethal-service situations, unexpected corrosion damage may lead to loss of life.
To avoid or mitigate adverse consequences of corrosion, repair or replacement of sensitive materials and equipment must occur before failure. However, unnecessary repairs or replacement can be costly. Accordingly, there has been a considerable amount of research into devices and procedures used to predict, detect and quantify corrosion. By detecting corrosion or the extent of corrosion, repairs or replacement of sensitive materials and equipment can be delayed until such detection indicates that sufficient corrosion has occurred to warrant maintenance.
One device proposed for the detection of corrosion is that of a thin metal film corrosion indicator. It has long been known that thin metal films exhibit distinctive changes in appearance and electrical properties when undergoing corrosion. See, e.g., Rohrback, G. H. and Roller, D., Development of Thin Metal Film Corrosion Indicators, Corrosion, Vol. 16, No. 8, August 1960, at 105-10. One common application is to deposit a thin metal film on a support with two contacts to the thin metal film. The thin metal film is often sensitized, e.g., artificially contaminated with a salt layer, to promote more even corrosion across the metal film. The two contacts may be fit to a hermetic seal feed-through connector. The hermetic seal feed-through connector ensures that the two contacts are not exposed to a corrosive environment. An electrical meter is then attached to the two contacts to detect resistance in the metal film. The electrical meter may be remote from the corrosion indicator and may monitor several corrosion indicator stations through the use of a station selector switch. Alternatively, the electrical meter may be portable and attached to each corrosion indicator individually for resistance measurement.
While such electrical corrosion indicators are useful, they are also cumbersome. It may not be practicable to maintain connection between the electrical meter and the corrosion indicator, e.g., the corrosion indicator may be desirably attached to a device in motion. In addition, limited accessability or spacial considerations may make it difficult to attach an electrical meter to the corrosion indicator in use.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative apparatus and methods for detecting corrosion.
One embodiment of the invention includes a corrosion sensor. The corrosion sensor includes a support, a power source contained on the support, a visual indicator contained on the support and coupled to the power source, and an electrode having an electrical resistance contained on the support and coupled to the power source and the visual indicator. Changes in the resistance of the electrode facilitate a display on the visual indicator. The display on the visual indicator includes either changes in color or changes in brightness. Such changes in color or brightness may be used to display an alpha-numeric message or other symbolic image in response to the change in resistance.
Another embodiment of the invention includes a method of monitoring corrosion of a material of interest. The method includes placing a corrosion sensor in an environment containing the material of interest. The corrosion sensor includes a support, a power source contained on the support, a visual indicator contained on the support and coupled to the power source, and an electrode having an electrical resistance contained on the support and coupled to the power source and the visual indicator. Changes in the resistance of the electrode facilitate a display on the visual indicator. The display on the visual indicator includes either changes in color or changes in brightness. The method further includes monitoring changes in the display on the visual indicator. The changes in the display on the visual indicator are indicative of corrosion of the material of interest.
A further embodiment of the invention includes a method of monitoring corrosion of a material of interest. The method includes placing a corrosion sensor in an environment containing the material of interest and directing an electromagnetic radiation source at the corrosion sensor. The electromagnetic radiation source activates a display on the corrosion sensor. The display is responsive to corrosion-induced changes in electrical resistance of the corrosion sensor. The method further includes monitoring changes in the display on the corrosion sensor. The changes in the display on the corrosion sensor are indicative of corrosion of the material of interest.
Other embodiments of the invention include corrosion sensors and methods of varying scope.